Flying to destinations beyond the Northwest is a change from Alaska Airlines’ original request to run Horizon Air commuter flights per week at the airport, primarily to Portland and Spokane.

Also different: The airline will use 737-800 jets. The airline initially proposed using only smaller Bombardier Q400 turboprops.

Alaska proposes to run 98 flights per week in and out of the Snohomish County-owned airport within five years, according to a proposal it submitted to the Federal Aviation Administration on Thursday. Included are 42 flights between Everett and Portland per week on the Bombardiers.

Allegiant Air also has asked to operate flights to Las Vegas from Paine Field and possibly other West Coast destinations. Allegiant is based in Las Vegas, Alaska in Seattle. Both airlines first approached Snohomish County in 2008.

Snohomish County still must build a terminal at Paine Field to accommodate passengers. That process would take more than a year, according to county officials.

The airport was built in the late 1930s. It primarily has served military operations, Boeing service and test flights, aircraft maintenance businesses and small, private planes. Except a short period around 1950 and briefly in the late 1980s, Paine Field has not had commercial airline service.

It’s unclear if or how Alaska’s latest proposal would affect the federal environmental ruling. The earlier plans would have brought 23 flights per day, combined between the two airlines, to Paine Field within five years.

The current plan would bring about 17 daily flights to the airport in the same time frame — fewer overall, but some with larger, louder jets.

“We’ve asked the FAA to determine if any further environmental review is needed because of our proposed jet service,” Alaska spokesman Paul McElroy said.

Allen Kenitzer, a spokesman at the FAA’s regional office in Renton, provided only a brief comment.

“We have in fact received a letter from Alaska Airlines and are reviewing it,” he said in an email.

Officials also said, however, that if another airline were to serve the airport, then Alaska would again be interested.

Allegiant officials have remained interested throughout.

Recent projects at Sea-Tac include the completion of a third runway; a remodeled terminal building, and Sound Transit’s extension of Link light rail to the airport.

Bellingham, about an hour’s drive north of Everett, is undergoing a $17 million expansion of its terminal.

“They have made Sea-Tac more convenient for travelers and they’ve better equipped Bellingham to handle more traffic,” McElroy said. “Serving a third airport between those cities undercuts our ability to provide travelers with the lowest fares possible.”

At the same time, he said, “the airline industry is extremely competitive, and we take all threats very seriously.”

In the first year Alaska would run 14 weekly round trips to Las Vegas, Honolulu and Maui, Hawaii on the 737-800s and 21 weekly round-trips to Portland. Not all destinations would be served daily.

By the fifth year of operations, Alaska would fly 49 weekly round-trip flights, or 98 one-way flights in and out of Paine Field. This would include 28 round-trips to Las Vegas, Honolulu, Maui, Los Angeles, Phoenix and San Diego with 737-800s, plus the 21 weekly round-trips to Portland using Q400s.

Opponents of commercial service say opening Paine Field to commercial service could increase noise and traffic in surrounding communities. Supporters say flights could help the economy by bringing jobs to the county and convenience for travelers.